A Connectomic Atlas of the Human Cerebrum-Chapter 13: Tractographic Description of the Inferior Fronto-Occipital Fasciculus

Abstract

The inferior fronto-occipital fasciculus (IFOF) is a large white matter tract of the human cerebrum with functional connectivity associated with semantic language processing and goal-oriented behavior. However, little is known regarding the overall connectivity of this tract. Recently, the Human Connectome Project parcellated the human cortex into 180 distinct regions. In our other work, we have shown these various regions in relation to clinically applicable anatomy and function. Utilizing Diffusion Spectrum Magnetic Resonance Imaging tractography coupled with the human cortex parcellation data presented earlier in this supplement, we aim to describe the macro-connectome of the IFOF in relation to the linked parcellations present within the human cortex. The purpose of this study is to present this information in an indexed, illustrated, and tractographically aided series of figures and tables for anatomic and clinical reference.

FIGURE 1.

Simplified tract map showing the structural connections that integrate within the IFOF. Connections between cortical areas are color-coded based on the parcellation of origin (eg, black arrows indicate structural connections from origin V3a to areas 9m, 10d, 10pp, and a47r). Note that arrows are not meant to imply the direction of information transmit.

FIGURE 2.

IFOF connections from areas 9p, 9a, and 9m in the left cerebral hemisphere. Area 9 regions have connections to early visual processing areas including V1, V2, and V3 in this subject brain. Area 9p demonstrates structural connections to area V6 as well. Connections are shown on T1-weighted magnetic resonance (MR) images in the A-E, sagittal and F, axial planes. All parcellations are indicated with white arrows and corresponding labels. The IFOF courses inferiorly to pass adjacent to the insula in the extreme capsule before reaching its terminations in the occipital lobe.

FIGURE 3.

IFOF connections from area V1 in the left cerebral hemisphere to parcellations in the frontal pole and inferior frontal gyrus. Connections are shown on T1-weighted MR images in A-C, sagittal and D, axial planes. Area V1 has connections to regions 45, 47S, 47L, a47r, 11L, a10p, and p10p in this subject brain. All parcellations are indicated with white arrows and corresponding labels. The IFOF courses anteriorly to pass adjacent to the insula in the extreme capsule before reaching its terminations in the frontal lobe.

FIGURE 4.

IFOF connections from FOP5 in the left cerebral hemisphere to early visual cortex areas. Connections are shown on T1-weighted MR images in the A-C, sagittal and D, axial planes. Area FOP5 has connections to regions V1, V2, and V3 in this subject brain. All parcellations are indicated with white arrows and corresponding labels.

FIGURE 5.

A-C, IFOF connections from area 8BL to early visual cortex parcellations in the left cerebral hemisphere. Connections are shown on T1-weighted MR images in the A and B, sagittal and C, axial planes. Area 8BL has connections to regions V2, V3, V3a, and V6 in this subject brain. D-F, IFOF connections from area 8BL to superior parietal lobe parcellations in the left cerebral hemisphere. Connections are shown on T1-weighted MR images in D and E, sagittal and F, axial planes. Area 8BL has connections to regions VIP, MIP, and IPS1in this subject brain. All parcellations in each panel are indicated with white arrows and corresponding labels.